An Oakland watchdog group said Tuesday it is suing major manufacturers and retailers, including Target and Amazon.com, for selling nap mats made with a toxic flame retardant that is also a known carcinogen.

The lawsuit is the latest legal move for the group, which last year put the companies on notice for selling or making similarly contaminated changing pads, crib mattresses and other items. While some of the manufacturers and retailers say they've started to change their practices, the Center for Environmental Health says it wants the courts to require swift action.

Many foam nap mats, which are widely used at places like day care centers, are doused with flame retardants linked to obesity, hormone disruption and infertility, according to the lawsuit. One of those flame retardants is chlorinated Tris, a carcinogen that was banned more than 30 years ago from children's pajamas, the group says.

These chemicals are released into the air that infants and toddlers inhale as they doze on the mats, said Caroline Cox, the center's research director.

"Kids are sleeping on them with their nose practically right up against the mat," she said.

According to a report released by the center Tuesday, a Duke University scientist found flame retardants in 22 out of 24 nap mats that researchers bought or borrowed in California, New York, Connecticut, Massachusetts and other states.

The Center for Environmental Health used that information as the basis of lawsuits filed Friday in Alameda County Superior Court against the following vendors and sellers of nap mats: Target, Amazon.com, Lakeshore Learning, Venture Products and Peerless Products.

According to the lawsuit, the companies illegally failed to inform consumers that the products contain chlorinated Tris, which was banned from pajamas in 1979.

That omission violates Proposition 65, the state's consumer protection law, which requires warning labels on products with certain toxicants, the group said.

The group said it can only sue sellers and makers of items with chlorinated Tris, because the other flame retardants found are not subject to Prop. 65.

Jessica Deede, a Target spokeswoman, did not comment on the lawsuit except to say, "We abide by all state and federal laws, and expect our vendors to do the same." Amazon did not return a request for comment.

Halting sales

Toys R Us, which owns Babies R Us, said it is discussing the lawsuit's claims with its suppliers, and some retailers, such as Walmart and Lakeshore Learning, have said they would stop selling products with chlorinated Tris.

The Center for Environmental Health is suing to legally ensure they stick to their promise, Cox said.

Flame retardants have been controversial because of a 1975 California requirement that polyurethane foam in upholstered furniture and some children's items resist a small flame for 12 seconds.

Many nap mats carry tags that say they comply with California's flammability law, known as Technical Bulletin 117. But while TB-117 regulates booster seats, infant mattresses and other children's products, it doesn't apply to nap mats.

Manufacturers routinely add flame retardants to items that aren't included under the 1975 law. Cox said it is unclear why the chemicals were added to nap mats.

Many studies have found that the chemicals do little to stop foam items from catching fire.

Flame retardants common

The 24 mats analyzed by the Duke researcher were bought from stores, online and in person. Some of them were also borrowed from child care centers.

Twenty-two contained at least one flame retardant, and 19 had two or more. They included chlorinated Tris, the carcinogen that is known to damage DNA; triphenyl phosphate, which is linked to lower sperm production; and Firemaster 550, a mix of chemicals that cause obesity and disrupt hormones in lab animals.

The effects are "a concern because kids are young, they're growing and developing, their hormones are what shape that growth and development," Cox said. "But also because of the way hormones work, a very small amount of the chemical can have a large effect."

California is revising its flammability law. Connecticut, Maine, Maryland, Massachusetts, New Jersey, Vermont and Washington are all considering legislation to restrict flame retardants.

Nap mats with flame retardants

These mats sold in California contained flame retardants, according to the Center for Environmental Health. Retailers appear in parentheses:

Tips for parents

Feeling uneasy about the mat you just got for your toddler? Laying a blanket over the surface may keep some of the flame retardants from spreading, but "it certainly wouldn't stop the exposure," says Caroline Cox of the Center for Environmental Health.